Grain carbohydrate composition and genetic variation in bold grained rice (Oryza sativa L.) genotypes of Assam.

摘要

Hard-working rural people of Barak Valley Zone in Assam, India, prefer tasty bold grained rice despite their low yields. These rice genotypes are slowly digested and remain longer in stomach unlike the fast digestible medium and fine grained high-yielding varieties (HYVs) of rice developed so far by breeding. The present experiment was designed to study the carbohydrate components of 47 bold grained rice genotypes and their genetic variation in comparison to two high yielding controls, namely Ranjit and Monohar Sali. The mean range of the carbohydrate components, i.e. starch content (g/100 g of oven dry sample), amylose content (% of starch) and amylopectin content (% of starch) varied from 65.63 to 79.78, 15.25 to 25.56 and 74.44 to 84.75, respectively. The mean total soluble sugar content (g/100/g of oven dry sample), total reducing sugar content (g/100 g of oven dry sample) and total non-reducing sugar content (g/100 g of oven dry sample) varied from 0.35 to 1.14, 0.103 to 0.363 and 0.279 to 0.935, respectively, in bold grained rice genotypes. The difference between phenotypic and genotypic coefficient of variation was very small for all the carbohydrate component characters, indicating little influence of environment in their expression. In the present investigation, high heritability associated with high genetic advance was found in the characters total soluble sugar content, total reducing sugar and total non-reducing sugar content, indicating predominant role of additive gene action in their inheritance. Breeding method based on progeny testing and mass selection could be useful in improving these traits. High heritability along with moderate genetic advance was observed in the character amylose content. Judicious application of pure line selection may be effective for improving amylose content. But high heritability with low genetic advance was recorded for starch and amylopectin contents. This indicated the predominant role of non-additive gene action (dominance and epistasis) in the inheritance starch and amylopectin contents.